1. Field of the Invention
The present invention relates generally to laryngeal prostheses for enabling alaryngeal speech by a patient whose larynx has been removed.
2. Description of the Prior Art
Human speech is enabled by the passage of expired air from the lungs up through the trachea to pass through the laryngeal cavity and be exhaled through the mouth. The laryngeal cavity contains a plurality of adjustably-tensioned mucous membranes, or vocal cords, stretched thereacross. During such exhalation, these membranes are caused to vibrate and produce audible sounds by a flow of expired air therearound, and differences in pitch are achieved by muscles which adjust the tension of these vibratory membranes.
Since the larynx is susceptible to trauma, injury, and various diseases, a laryngectomy may have to be performed to remove a person's larynx. However, such removal of the larynx also removes the patient's primary sound-producing vibratory elements and therefore sharply reduces the patient's ability to produce coherent audible sounds.
It is known to provide such post-laryngectomy patients with a laryngeal prosthesis by which the flow of expired air may be selectively diverted to an alternate body cavity capable of producing an audible sound. This type of alternative speech is generally referred to as being "alaryngeal" because it enables the patient to produce coherent audible signals similar to those produced by the larynx.
Earlier known attempts to produce such a laryngeal prosthesis have generally contemplated that the flow of expired air be diverted from the trachea to the cervical esophagus. However, this concept has been complicated by the danger of providing a cervical esophageal fistula in the patient's neck due to the risk of rupturing one of the carotid arteries, the problem of saliva leakage, and the general requirement that the patient's neck have not been previously violated by surgery or irradiation.
One example of a prior art laryngeal prosthesis requiring a cervical esophageal fistula is taught by Taub U.S. Pat. No. 3,747,127 which discloses a device having a first tube adapted to be inserted into a tracheal fistula and a second tube adapted to be inserted into a cervical esophageal fistula. A valve arranged between the tubes permits the patient to inhale and exhale through a main port. This valve may be moved in response to increased breathing levels to divert a flow of expired air from the tracheal fistula to the esophageal fistula to enable alaryngeal speech by the patient. However, in addition to the disadvantage of having to provide a cervical esophageal fistula, this device does not appear to enable the patient to cough freely through the main port without manually adjusting the valve.
Additional isolated structural details of other generally pertinent prior art devices may be shown in Capra U.S. Pat. No. 3,066,674, Roberts U.S. Pat No. 2,405,850, Brehm U.S. Pat. No. 2,198,241, Riesz U.S. Pat. No. 2,024,601, McKesson U.S. Pat. No. 1,922,385, Riesz et al. U.S. Pat. No. 1,901,966, Riesz U.S. Pat. No. 1,836,816, Burchett U.S. Pat. No. 1,867,350, and McKesson U.S. Pat. No. 1,633,705.
Desirably a laryngeal prosthesis should enable a patient to freely inhale, exhale and cough, and speak alaryngeally by selectively diverting expired air to an alternate body cavity capable of producing audible vibrations.